U.S. patent application number 10/527176 was filed with the patent office on 2005-12-22 for method and device for drafting at least one sliver.
Invention is credited to Dammig, Joachim.
Application Number | 20050278900 10/527176 |
Document ID | / |
Family ID | 30469693 |
Filed Date | 2005-12-22 |
United States Patent
Application |
20050278900 |
Kind Code |
A1 |
Dammig, Joachim |
December 22, 2005 |
Method and device for drafting at least one sliver
Abstract
Disclosed is a method for drafting at least one sliver (FB) by
means of a regulated spinning machine, particularly a carding
machine or drawing frame, comprising pairs of rollers (2a, 2b, 3a,
3b, 4a, 4b) which are disposed one behind another and upstream of
which the cross section of the at least one sliver is measured. The
inventive method is characterized by the fact that at least one
roller (2a, 3a) of a first pair of rollers (2a, 2b, 3a, 3b) is
triggered via a first regulating circuit while at least one roller
(4a) of a second pair of rollers (4a, 4b) is triggered via a second
regulating circuit based on the measuring signals. Also disclosed
is a device for carrying out the inventive method.
Inventors: |
Dammig, Joachim;
(Ingolstadt, DE) |
Correspondence
Address: |
DORITY & MANNING, P.A.
POST OFFICE BOX 1449
GREENVILLE
SC
29602-1449
US
|
Family ID: |
30469693 |
Appl. No.: |
10/527176 |
Filed: |
February 7, 2005 |
PCT Filed: |
June 11, 2003 |
PCT NO: |
PCT/EP03/06088 |
Current U.S.
Class: |
19/239 |
Current CPC
Class: |
D01H 5/42 20130101 |
Class at
Publication: |
019/239 |
International
Class: |
D01H 005/32 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 10, 2002 |
DE |
102 36 778.7 |
Claims
1. Method for the drafting of at least one fiber sliver (FB) by
means of a regulated spinning machine, particularly a carding
machine or draw frame comprising pairs of rollers (2a, 2b, 3a, 3b,
4a, 4b) which are disposed one behind another, whereby the mass
cross-section of the (at least one) fiber sliver is measured
upstream of the pairs of rollers (2a, 2b, 3a, 3b, 4a, 4b),
characterized in that based on the measuring signals, at least one
roller (2a, 3a) of a first pair of rollers (2a, 2b, 3a, 3b) is
actuated through a first auto-leveling circuit and at least one
roller (4a) of a second pair of rollers (4a, 4b) is actuated
through a second auto-leveling circuit.
2-29. (canceled)
Description
[0001] The invention relates to a method for drafting at least one
fiber sliver by means of a auto-leveling spinning machine,
particularly a carding machine or draw frame comprising pairs of
rollers which are disposed one behind another, whereby the
cross-section of the mass of the (at least one) fiber sliver is
measured upstream of the roller pairs. The invention furthermore
relates a device for the drafting of at least one fiber sliver by
means of at least one upstream and one downstream pair of rollers,
with at least one sliver cross-section measuring device upstream of
these pairs of rollers for the measuring of the cross-section of
the mass of the (at least one) fiber sliver.
[0002] Spinning machines such as cards or draw frames serve the
purpose of forming as uniform a textile material as possible from
the presented textile material. For this purpose the spinning
machines often comprise a auto-leveling draw frame in order to
actuate drafting elements installed one after the other in the
direction of sliver movement in function of detected fluctuations
based on the sliver cross-section fluctuation measured before the
draw frame. In draw frames these drafting elements are constituted
e.g. by several pairs of rollers installed one after the other,
between which the fiber sliver or slivers is clamped along the
respective so-called nip line in the direction across the sliver.
Since the pairs of rollers have different circumferential speeds
that increase in the direction of sliver movement, the fiber bundle
consisting of one or several fiber slivers is drawn and evened out.
In most cases a second sliver cross-section measuring device is
provided at the output of the draw frame to produce an
acknowledgment in a closed auto-leveling circuit or to control the
evening out and possibly to trigger a machine stop in case of
excessive sliver thickness fluctuations.
[0003] Mostly mechanical scanning devices have emerged for
scanning. For example, the Rieter Draw Frame RSB D30 has a pair of
scanning disks with axes that are parallel to each other before the
drawing equipment, whereby one scanning disk is fixed in place and
the other scanning disk is mobile. The fiber sliver or slivers are
guided in a gap between a circumferential groove of the first
scanning disk and a circumferential ring of the second scanning
disk, whereby the mobile scanning disk is moved away in function of
the mass fluctuations of the fiber sliver or slivers. The excursion
movements are converted by a signal converter into electrical
voltage values and are transmitted to an auto-leveling processor to
actuate the pairs of rollers of the drawing equipment.
[0004] Especially in the case of spinning machines where the
scanning gear and the pairs of rollers are connected to each other
e.g. via a differential gear, the adjustable frequency range is
relatively limited with regard to sliver cross-section
fluctuations. Because of great mass inertia of such an arrangement
a desired adjustment is not possible over a wide frequency range of
long-wave fluctuation (so-called A % values) up to auto-leveling
lengths of a few centimeters at high delivery speeds. Furthermore
the wear of machine parts caused by the great band width of the
signal content and the acceleration of large masses connected to it
as well as energy consumption are relatively high.
[0005] FIG. 1 shows auto-leveling drafting equipment in which a
fiber sliver FB runs through a mechanical sliver cross-section
measuring device 8 and is then guided into drafting equipment
constituted by three pairs of drafting rollers 2a, 2b, 3a, 3b, 4a,
4b. The sliver cross-section measuring device 8 is constituted by
two scanning disks already described earlier.
[0006] One of the two scanning disks is coupled to a clock
generator 11 producing a given number of cycles or impulses per
revolution of this scanning disk. The mobile scanning disk is
furthermore connected to a signal converter 10 which converts its
excursions into electrical voltage values. These voltage values are
transmitted to a measured-value delaying unit 12 which in addition
receives a number of cycles from the clock generator 11,
representing a measure of the speed of the fiber sliver FB running
through the sliver cross-section measuring device 8. In accordance
with these cycles of the clock generator 11, the voltage values are
held back in the measured-value delaying unit 12 which represents
an electronic memory in form of a FIFO (First-in-First-Out) in
function of the distance covered by the fiber sliver between the
cross-section measuring device 8 and the drafting equipment. When
the fiber sliver reaches the fictitious drafting point in the
drafting field of the drafting equipment with the sliver segment to
be auto-leveled, the corresponding measured value is released by
the measured-value delaying unit 12 and a corresponding adjustment
is made in function of the respective measured value. The distance
between the measuring point of the pair of scanning rollers and the
drafting point is called the auto-leveling application point. For
this the measured-value delaying unit 12 transmits the measured
values to an algorithm unit 13 which transmits the rotational speed
of the drafting equipment rollers concerned and the corresponding
information to an auto-leveling drive 22 on basis of the desired
drafting setting and set machine parameters. This auto-leveling
drive 22 drives a differential gear 23 which drives the fixed
scanning disk of the cross-section measuring device 8, the lower
roller 2a of the pair of input rollers as well as the lower roller
3a of the pair of central rollers. The differential gear 23
receives a basic rotational speed from a main motor 14, and this
speed can be adjusted via a rotational-speed adjusting unit 15
intercalated between the main motor 14 and the differential gear
23.
[0007] The main motor 14 in turn drives the lower roller 4a of the
pair of output rollers directly, so that a constant sliver running
speed is obtained. Accordingly, merely the pair of input rollers
and the pair of central rollers are used for auto-leveling.
[0008] It is the object of the present invention to further develop
the method and device of the type indicated initially in such
manner that a precise drafting of one or several fiber slivers is
achieved.
[0009] This object is attained through the method indicated
initially in that at least one roller of the first pair of rollers
is actuated on basis of the measuring signals via a first
auto-leveling circuit and in that at least one roller of a second
pair of rollers is actuated via a second auto-leveling circuit.
[0010] This object is furthermore attained in a device of the type
indicated initially by means of two auto-leveling circuits, whereby
at least one roller of a first pair of rollers can be actuated via
the first auto-leveling circuit and a roller of a second pair of
rollers via the second auto-leveling circuit.
[0011] The advantages of the invention can be seen especially in
the fact that the scanning signals are processed before the
drafting equipment in at least two auto-leveling circuits in order
to thus increase the flexibility and the precision of the actuation
of the drafting elements or rollers. The (at least two)
auto-leveling circuits can react in this case to different signal
contents and thus take over a distribution of the actuation tasks.
In this manner at least one roller of the first pair of rollers and
at least one roller of a second pair of rollers which can be
uncoupled at least partially with respect to their mass inertia
actuation can be actuated.
[0012] It is especially preferred to subdivide the measuring signal
portions of the (at least one) cross-section measuring device with
respect to its frequency into at least two frequency ranges. Based
on the appurtenance of measuring signal portions to different
frequency ranges, the rollers of different pairs of rollers can
then be actuated. In this manner the auto-leveling is also divided
within the frequency range. Thereby every frequency band can be
divided among machine elements according to its energy
requirements.
[0013] The possibility exists of using low-frequency measuring
signal portions, i.e. longer-wave sliver cross-section
fluctuations, to control machine elements or drive elements with
greater mass moment of inertia. Therefore higher-frequency
measuring signal portions can be used to control drive elements
with lower mass moment of inertia. Due to the low mass moment of
inertia these machine elements can be accelerated or braked more
quickly so that these machine elements can also follow the
higher-frequency measuring signal portions. Overall a more precise
auto-leveling is achieved thereby, whereby longer-wave as well as
shorter-wave fluctuations of sliver cross-sections can be
auto-leveled optimally.
[0014] It benefits signal processing if the measuring signal
portions of the sliver cross-section measuring device upstream of
the drafting equipment are assigned to at least one lower and one
upper frequency range. In order to be able to use all frequency
portions of the sliver cross-section fluctuations, the lower and
the upper frequency ranges are preferably close together, and it is
especially preferred if they overlap without a gap. The upper
frequency range is preferably selected so that an essentially
loss-free processing of the machine elements with lower mass moment
of inertia is possible. It is also preferable to select the lower
frequency range so that an essentially loss-free processing of the
machine elements with higher mass moment of inertia is
possible.
[0015] It has been shown to be advantageous if the lower frequency
range comprises frequencies within the range of approximately 1 to
3 Hz and the upper frequency range frequencies in the range of 3 to
100 Hz. These frequency ranges should however not be regarded as
being fixed, but can be advantageously selected or adjusted
depending on the auto-leveling draw frame and/or material to be
drafted or on other parameters. Nor is the mentioned maximum
frequency of 100 Hz a technologically imposed magnitude. Depending
on the design of the drafting equipment or of the participating
masses to be accelerated, lower or higher limit values are also
possible.
[0016] Different possibilities exist for the assignment of
different measuring signal portions to different frequency ranges.
In preferred examples of embodiments frequency filters produced in
form of hardware and/or software are used for this purpose.
[0017] In the first auto-leveling circuit a roller of the pair of
input rollers and one of the pair of central rollers is preferably
actuated, while a roller of the pair of delivery rollers is
actuated in the second auto-leveling circuit. Contrary to the state
of the art described above, the pair of delivery rollers is thus
also used for auto-leveling. It is therefore possible to auto-level
possible sliver cross-section fluctuations of higher frequency by
actuating the pair of delivery rollers due to its lower mass
inertia. Since this auto-leveling at output does not produce any
additional drafting in the medium, the known disadvantages of
output auto-leveling, consisting in particular in variation of the
sliver depositing speed and the resulting occurrence of problems in
these known machines with regard to clean deposit of the drafted
fiber sliver in a spinning can are avoided. The described preferred
variant of the invention provides however in principle an input
auto-leveling with superimposed output auto-leveling. The basic
drafting and the auto-leveling of low-frequency sliver fluctuation
up to e.g. 3 Hz are provided by means of the low-frequency
auto-leveling which is in principle that of the known auto-leveling
e.g. in the Rieter draw frame RSB D30. The upper-frequency band is
then modulated up to that drafting by means of the higher-frequency
auto-leveling in the draw frame. This higher-frequency
auto-leveling represents a precise CV % auto-leveling, whereby the
CV % value is defined as CV %=s/x*100. Here CV % is the variation
coefficient (percentage of sliver unevenness), s is the standard
deviation and x is the mean value of all samples.
[0018] The especially preferred embodiment of the invention
described above is therefore characterized by superimposed
auto-leveling via the output drafting equipment or pair of
rollers.
[0019] Actuation takes place in the first and second auto-leveling
circuit in such manner that the point of auto-leveling application
or point of drafting in the drafting field formed by the pair of
central rollers and the pair of delivery rollers is identical for
both auto-leveling circuits. This means that the point of drafting
is identical for both auto-leveling circuits and no delay of
measured value of the two auto-leveling circuits relative to each
other (by means of a FIFO memory or similar device) is
required.
[0020] Alternatively or in addition to the actuation of a roller of
the pair of delivery rollers, at least one roller of a pair of
calendar rollers located downstream of the drafting equipment can
be provided in the second auto-leveling circuit or also in a third
auto-leveling circuit. This makes it possible, for example, to
coordinate the circumferential speed of the pair of delivery
rollers and of the pair of calendar rollers with each other in
order to create synchronous running in such manner that no drafting
occurs between these two pairs of rollers. It is therefore not
absolutely necessary, in using such a design, for the drafted fiber
sliver to leave the draw frame at a constant output speed.
[0021] Installation of a low-pass filter before a first target
value step in the first auto-leveling circuit is especially
preferred. The voltage signals released preferably by the
measured-value delaying device at first go through this (at least
one) low-pass filter before being switched up to a target value
step in the first auto-leveling circuit (actual values). This
target value step furthermore preferably receives the rotational
speed of a main motor (target values) determined by a tachometer
generator in order to determine a target value for a first
auto-leveling drive from these switched-up signals. The first
auto-leveling drive then drives, as in the state of the art, a
differential gear which drives the mechanical scanning gear as well
as the lower rollers of the input and the central pairs of
rollers.
[0022] It is especially preferred to install at least one high-pass
filter in the second auto-leveling circuit upstream of a second
target value step. In addition to the high-frequency voltage
signals of the sliver cross-section measuring device (actual
values) the voltage signals (target values) representing the
rotational speeds of the main motor are preferably also switched up
the second target value step. A second auto-leveling drive serving
to drive machine elements with lower mass inertia is preferably
provided downstream of the output of the second target value step.
Such a machine element is preferably a roller of the pair of
delivery rollers.
[0023] The second auto-leveling drive preferably drives a second
differential gear which preferably receives its basic rotational
speed also from the main motor. The second auto-leveling drive thus
oscillates symmetrically around the rotational speed 0 in function
of the thick and thin spots of the (at least one) fiber sliver.
[0024] Alternatively, the second auto-leveling drive provided in
the second auto-leveling circuit for the leveling of the
high-frequency measuring signal portions may be designed for direct
actuation of at least one roller of the corresponding pair of
rollers, preferably the pair of delivery rollers and/or pair of
calendar rollers. In this embodiment no differential gear is
therefore required in the second auto-leveling circuit. Precise
driving of the auto-leveling drive which does not oscillate around
the rotational speed 0 is of course required in this case.
[0025] In an advantageous alternative embodiment of the invention
the lower frequency range in the first auto-leveling circuit is
delimited by a low-pass filter of at least first order, whereby the
signals in the upper frequency range are formed from the original
measuring signal by subtraction of the low-pass filter signal
output. Amplitude and phase errors of the original measuring
signals in the upper frequency range or in the second auto-leveling
circuit that were locked out by the low-pass filter or were allowed
to pass defectively are hereby preferably taken into account.
[0026] In an alternative embodiment the upper frequency range is
limited downward by a high-pass filter of at least first order,
whereby the signals in the lower frequency range are formed by
subtracting the high-pass filter signal output from the original
measuring signal. Thereby possible amplitude and phase errors are
automatically compensated for, i.e. no amplitude or phase jumps
occur.
[0027] In an advantageous variant of the invention machine elements
comprising the drafting equipment elements and having an overall
higher moment of mass inertia than machine elements with an overall
lower moment of mass inertia are used as low-pass filter. Parts of
the machine with relatively high moment of mass inertia are thereby
themselves used as frequency-separating low-pass filter. The
measuring elements run in that case through the first auto-leveling
circuit and are furthermore branched off into the second
auto-leveling circuit. To control the low-pass filter effect a
tachometer generator can be advantageously provided to measure the
rotational speeds of at least one of the drive elements, in
particular of a roller, whereby this roller is part of the machine
elements with high moment of mass inertia.
[0028] In a special embodiment of the variant described above the
output of a first target value step in the first auto-leveling
circuit is connected to the input of a target value step in the
second auto-leveling circuit. In this embodiment it is not
necessary to split the measuring signal following the
measured-value delaying unit by means of a low-pass and a high-pass
filter. The measuring signal of the sliver cross-section measuring
device can rather be switched up to the target value step in the
first auto-leveling circuit following conversion in the signal
converter. The output signal of this target value step serves on
the one hand to produce a control signal for the drive elements in
the first auto-leveling circuit, (the assistance in this by a first
auto-leveling drive and a differential gear being especially
preferred) and on the other hand in form of a target value as input
signal for a target value step in the second auto-leveling circuit.
The actual value for the second target value step is here produced
preferably by measuring the frequency portions converted by the
machine into amplitude and phase in the first auto-leveling
circuit, e.g. by connecting a tachometer generator to one of the
central rollers to produce the above-mentioned actual values for
the second target value step. The high-pass filter of the second
auto-leveling circuit is thus realized in principle by the machine
itself without requiring any other filters, whereby the frequency
portions of lower frequencies that the machine can utilize in the
first auto-leveling circuit are measured and are subtracted from
the measuring signals in the second target value step to be
processed overall and comprising all frequencies.
[0029] The voltage signals produced by a tachometer generator can
be advantageously switched up to the input of the target value step
of the second auto-leveling circuit in function of the rotational
speeds of e.g. a central roller or an input roller. These voltage
values of the tachometer generator can be synchronized with a clock
generator connected to the sliver cross-section measuring device
before they are switched to the input of the target value step of
the second auto-leveling circuit.
[0030] Instead of merely one sliver cross-section measuring device,
it is also possible to use several such measuring devices before
the drafting equipment.
[0031] The (at least one) sliver cross-section measuring device may
be e.g. in form of a mechanical scanning device. Alternatively or
in addition, a microwave sensor with a resonator can be used.
[0032] Advantageous further developments of the invention are
characterized by the characteristics of the sub-claims.
[0033] Different examples of embodiments of the invention are
explained in further detail below through the figures.
[0034] FIG. 1 shows a schematic circuit arrangement according to
the state of the art,
[0035] FIG. 2 shows a schematic circuit arrangement according to
the first embodiment of the invention,
[0036] FIG. 3 shows a schematic circuit arrangement according to a
second embodiment of the invention,
[0037] FIG. 4 shows a schematic circuit arrangement according to a
third embodiment of the invention and
[0038] FIG. 5 shows a schematic circuit arrangement according to a
fourth embodiment of the invention.
[0039] The different embodiments of the invention to be discussed
below are starting from the state of the art shown in FIG. 1. Other
drive principles as well as circuit arrangements are however also
covered by the inventive idea.
[0040] According to FIG. 2 the sliver cross-section fluctuations
are determined mechanically by means of a sliver cross-section
measuring device 8. The term "sliver cross-section fluctuations" is
to be understood within the framework of this invention also as
sliver mass fluctuations, sliver thickness fluctuations, sliver
volume fluctuations or similar concepts. The measured values of the
sliver cross-section fluctuations are converted in a signal
converter 10 into digital voltage signals and are transmitted to a
measured-value delaying unit 12 which is realized e.g. in form of a
hardware or software FIFO (First-In-First-Out) memory. The sliver
cross-section measuring device 8 is furthermore followed by a clock
generator 11 producing an impulse in function of a given fiber
sliver segment length, e.g. 1.5 mm and transmits the impulse number
also to the measured-value delaying unit 12. Depending on the
running time of the fiber sliver FB from the sliver cross-section
measuring device 8 to the desired drafting point or auto-leveling
starting point in the drafting equipment consisting of the pairs of
drafting roller 2a, 2b, 3a, 3b, 4a, 4b the delayed voltage signals
are transmitted from the measured-value delaying unit 12 to a
low-pass filter 20 in a first auto-leveling circuit. After going
through the low-pass filter which may allow the passage of
frequencies within a frequency range of e.g. Approximately 0 to
approximately 3 Hz, the suitably filtered voltage signals are
transmitted to a first target-value step 21 in the first
auto-leveling circuit target values. Furthermore a voltage value is
switched up by a tachometer generator 16 which determines the
rotational speed of a main motor 14 and converts it into a
corresponding voltage signal target values. The output of the
target-value step 21 is switched up to a first auto-leveling drive
22 which drives a first differential gear 23. The first
differential gear 23 receives the basic rotational speed from the
main motor 14 whose rotational speed can be set by a
rotational-speed setting unit 15.
[0041] The first auto-leveling drive 22 is preferably designed in
form of a servo drive producing a rotational control speed for the
differential gear 23 which is preferably in form of a planetary
gear. The differential gear 23, a scanning roller of the sliver
cross-section measuring device 8, the lower roller 2a of the pair
of input rollers as well as the lower roller 3a of the pair of
central rollers are driven at this controlled starting speed of the
differential gear 23. The rotational speeds of the rollers 2a and
3a are not necessarily equal. It is possible, for example, to drive
them at a fixed rotational speed ratio. The second auto-leveling
circuit according to the invention comprises a high-pass filter 30
at the input of which the voltage values of the measured-value
delaying unit 12 are given. The high-pass filter 30 filters the
voltage signals and may allow frequencies of e.g. approximately 3
Hz to approximately 100 Hz to pass. The thus filtered voltage
signals are switched up to a second target-value step 31 (actual
values). The second target-value step 31 receives furthermore the
rotational speed of the main motor 14 (target values) converted
into voltage values by the tachometer generator 16. The second
target-value step 31 determines a control rotational speed from
these signals for a second auto-leveling drive, advantageously
again a servo drive. The second auto-leveling drive 32 drives a
second differential gear 33 of the second auto-leveling circuit,
whereby this second differential gear 33 also receives its basic
rotational speed from the main motor 14. The lower roller 4a of the
pair of delivery rollers is driven at this controlled starting
speed of the second differential gear 33. The two auto-leveling
circuits thus realize an input leveling with superimposed output
leveling, whereby the second auto-leveling drive oscillates
symmetrically around the rotational speed 0. Additional drafting is
not produced by the output leveling.
[0042] As shown in the embodiment shown in FIG. 2, the longer-wave
sliver cross-section fluctuations can be compensated for
sufficiently by the machine elements with greater mass inertia such
as the mechanical scanning gear of the sliver cross-section
measuring device 8, the first differential gear 23, rollers 2a, 3a.
The higher-frequency sliver cross-section fluctuation can be
compensated for by means of the output leveling by actuating the
roller 4a of the pair of delivery rollers. At the starting point of
auto-leveling the frequency ranges are again reunited, so that wear
of e.g. motor drive belts, caused by the great sliver width of the
signals, can be reduced. The wear caused by the acceleration of
great masses as well as increased energy consumption to drive these
masses which remains in part without effect in the state of the art
because of the impossibility of auto-leveling high-frequency sliver
cross-section fluctuations can also be reduced.
[0043] In the embodiment of FIG. 2 as well as in the analogous ones
of FIGS. 3 to 5 the auto-leveling processor comprises the
measured-value delaying unity 12, the low-pass filter 20, the
high-pass filter 30, the first target-value step 21 and the second
target-value step 31. These elements are reproduced in the software
in the auto-leveling processor.
[0044] The embodiment of FIG. 3 differentiates itself from that of
FIG. 2 in that it does not have its own high-pass filter to filter
the voltages representing the low-frequency sliver cross-section
fluctuations. The unfiltered voltage signals on the one hand and
the voltage signals filtered by a low-pass filter 20 as in FIG. 2
are switched on the other hand to a subtraction element 135 by the
measured-value delaying unit 12. The subtraction element 135
delivers the output values which only contain the high-frequency
signal portions of the sliver thickness fluctuations and transmits
these in form of target values to a second, multiplying
target-value step 131 of the second auto-leveling circuit. The
target values of this second multiplying target-value step 131 are
received by a tachometer generator 16 converting the rotational
speed of the main motor 14 into a corresponding voltage signal,
similarly as in the embodiment according to FIG. 2. The
functionality of the embodiment according to FIG. 3 is otherwise
analogous to the one of FIG. 2.
[0045] FIG. 4 shows a third embodiment of the invention. The first
auto-leveling circuit, with a first target value step 221, a first
auto-leveling drive 22 and a first differential gear 23 are
unchanged from the embodiment as in FIG. 2 (merely the low-pass
filter 20 is missing). An output leveling superimposed according to
the invention is realized in this embodiment in that the output of
the first target value step 221 is not only applied to the first
auto-leveling drive 22 but also as a target value to the second,
subtracted target value step 231 of a second auto-leveling circuit.
The actual values for this second target value step 231 are
determined from the voltage values produced by a tachometer
generator 116 which detects the rotational speed of the upper
roller 3b of the central pair of rollers in the embodiment shown.
The rotational speed of one of the rollers 2a, 2b, 3a for example
could also be scanned.
[0046] In other words, a high-pass filter is realized in the second
auto-leveling circuit by the machine itself, whereby the tachometer
generator 116 measures the frequency portions converted by the
machine in the first auto-leveling circuit into amplitude and
phase, i.e. measuring signal portions of relatively low frequency
in order to subtract them from the overall signal which contains
all the frequency portions in the second target value step 231.
[0047] As a result of the comparison between the subtraction of the
target and actual values, the second target value step 231
determines target values corresponding to the high-frequency
measuring signal portions for a second auto-leveling drive 32 which
produces a control speed for a second differential gear 33 from
this target value. The lower roller 4a of the pair of delivery
rollers is driven with this controlled starting speed of the second
differential gear 33. As a result the desired drafting changes are
obtained in the main drafting field formed by the pair of central
rollers and the pair of delivery rollers, so that the sliver
cross-section fluctuations of the entering sliver or slivers FB can
be leveled.
[0048] In the embodiment of FIG. 5, similarly to that of FIG. 2, a
low-pass filter 20 and a high-pass filter 30 are again provided to
divide the measured-signal portions of the sliver cross-section
measuring device 8 into low-frequency signal portions and
high-frequency signal portions. Of course several filters can be
provided for the respective frequency ranges, as also in the
similar embodiments described before. The essential difference in
the embodiment of FIG. 5 from that of FIG. 2 is that the control
speed produced by the second auto-leveling drive 32 is not given to
a differential gear but is switched directly to the lower roller 4a
of the pair of delivery rollers. It should be noted that of course
in this as in preceding embodiments, it is also possible to drive
the upper rollers of the different pairs of rollers. By actuating
the roller 4a directly the second differential gear can be omitted.
In this embodiment a coupling of input leveling to output leveling
must however be omitted. The output leveling can rather produce
additional drafting by means of the second auto-leveling drive so
that the delivery speed is not necessarily constant. In that case
the possibility is given that the second auto-leveling drive 32 may
drive in addition pair of calendar rollers or a draw-off device
downstream of the drafting equipment so that the pair of delivery
rollers and the pair of calendar rollers may convey the fiber
sliver synchronously.
[0049] The invention can also be used with individual drives in
spinning machines. It is essential that sliver cross-section
fluctuations from signals received before the drafting equipment is
leveled in at least two auto-leveling circuits so as to be able to
take into account in particular the different moments of inertia of
different machine elements in these auto-leveling circuits. Thereby
a frequency band width enlargement can be obtained in leveling
drafting of the (at least one) fiber sliver.
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